A modern integrated circuit (IC) must meet very stringent design and performance specifications. In many applications for communication devices, transmit and receive signals are exchanged over communication channels. These communication channels include impairments that affect the quality of the signal that traverses them. One type of IC that uses both a transmit element and a receive element is referred to as a serializer/deserializer (SERDES). The transmit element on a SERDES typically sends information to a receiver on a different SERDES over a communication channel. The communication channel is typically located on a different structure from where the SERDES is located.
The SERDES transmitter and the SERDES receiver communicate using differential signals. Differential signals are those that are represented by two complementary signals on different conductors, with the term “differential” representing the difference between the two complementary signals. The two complementary signals can be referred to as the “true” or “t” signal and the “complement” or “c” signal. All differential signals also have what is referred to as a “common mode,” which represents the average of the two differential signals. High-speed differential signaling offers many advantages, such as low noise and low power while providing a robust and high-speed data transmission.
However, imperfections in the communication channel can cause mismatch between the two complementary signals. Minimizing this mismatch between the complementary signals can be done by independently adjusting the clock timing between the complementary signals at the transmitter or by using de-skewing circuitry in the receiver. Unfortunately, a skewed transmitter clocking scheme or de-skewing circuitry in the receiver are difficult to implement and are power intensive.
Therefore, it would be desirable to have a way to correct for the mismatch between the complementary signals in a differential signal communication methodology without using de-skewing circuitry in the receiver.